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I have a SLA battery:

12v
7Ah
C Rating 10

Is it true to say that when I use a charger, the charger needs to be less than half of 7Ah * 0.10?

My charger is rated for 750mA for 12v batteries.

So, I have 0.75A at 12v for charging. That is way under half of the 7Ah but just over half of the 7Ah * 0.10 which equals 0.70.

I am trying to not convulse the battery to the point it discharges.

Please send guidance. The maximum rated charge rate for this battery is 10% of the 7Ah.

De Funct
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1 Answers1

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C Rating 10

Do you mean a rating of 10C?

If so: 7Ah * 10C = 70 A

Is it true to say that when I use a charger, the charger needs to be less than half of 7Ah * 0.10?

Yes, that is a good guideline for lead acid batteries.

However, we warned that "C-rating" is a marketing tool, not an engineering parameter. A current of 10 C would discharge a battery in 6 minutes. The vast majority of batteries are damaged when discharged that fast and many batteries can't discharge that fast even if you try. For the sake of your battery, ignore the vendor's "C-rating" and discharge it at a reasonable rate. For example, 1 C for the typical LCO Li-ion battery, 2 C for a high-power Li-ion battery, and 0.1 C for the typical lead-acid battery.

Davide Andrea
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  • The CCA is 135 and it says C Rating of 10 on it. – De Funct Apr 01 '23 at 23:28
  • And yes. Rating of 10C. – De Funct Apr 01 '23 at 23:29
  • "The CCA is 135 and it says C Rating of 10 on it." There is a discrepancy between 135 A cold cranking (19C) and that " C Rating of 10". Is this some off-brand? – Davide Andrea Apr 01 '23 at 23:35
  • Made in Vietnam by MTD. It is some sort of a Lawn Tractor 12v battery. – De Funct Apr 01 '23 at 23:37
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    [This one](https://www.buildclub.com/product/bc0_428217293)? I don't see any C and 10 on it. – Davide Andrea Apr 01 '23 at 23:39
  • coulombs is not what the C indicates I am guessing here. I also think marketing is an overstatement as it costs $75.00 for this battery while others w/ the same rating and voltage-amperage cost very low. – De Funct Apr 01 '23 at 23:40
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    There are some very small writings on it. Let me triple check here. Maximum charge rate of 10% of Ah. Sorry. I started reading and got the charge rate and C Rating mixed up. But yes sir, the battery is exactly that one. It is a #725-17136. – De Funct Apr 01 '23 at 23:42
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    The Ah rating for most lead-acid batteries is defined at 1/20 C, so for 7 Ah it should produce 350 mA for 20 hours, although it's not good to discharge below about 20% SOC. And the Peukert Effect predicts a capacity of about 50% of rating when used at 1C (7 A). – PStechPaul Apr 02 '23 at 00:08